1. Field of the Invention
The invention relates to a method for inserting an insertion picture into a video picture, such as a television picture for example. The invention furthermore relates to a circuit arrangement which can be used to carry out a method for video picture insertion. In the case of video picture insertion, a further picture is displayed within the actual video picture. The signal for such an insertion picture can originate from a receiving unit in a television receiver, a video camera, a video recorder, a computer or another video signal source.
2. Description of the Related Art
In television receivers, this function, which is also referred to as picture-in-picture insertion (picture-in-picture, PiP), allows a further broadcast to be followed, in addition to the broadcast of a set program, via an excerpt from the television screen. The size of the excerpt and its position within the screen are often adjustable. The relative size of the excerpt in relation to the size of the visible screen determines how much of the picture content of the actual video picture is concealed by the insertion picture.
Circuit arrangements for video picture insertions contain, in addition to the input for the video signal, an additional input for the signal of the insertion picture. A changeover switch is used to change over between these signals in such a way that, in the case of a specific line and in the case of a specific line section, the matching signal is fed to the screen or another display device and the displayed picture is composed of the video picture with the insertion picture. Such a circuit arrangement is disclosed for example in DE 195 34 781 C1.
Video pictures can have different picture formats. The 4:3 format is used throughout the world for television pictures. The format detail stipulates that the ratio of the horizontal length to the vertical width is 4:3. The television corporations usually broadcast their programs in this 4:3 picture format. Another customary format is the 16:9 format, in which the aspect ratio is closer to that of cinema films.
Broadcasts having the 16:9 format are also transmitted in the 4:3 format. Customary television receivers receive these broadcasts in the same way as 4:3 broadcasts. Black bars at the top and bottom edges of the picture or else wide bars only at the bottom edge of the picture or only at the top edge of the picture then fill those regions of the television picture in the 4:3 format which are not utilized in the case of correctly-formatted reproduction of 16:9 broadcasts.
The windows for the insertion pictures in picture-in-picture applications also approximately have the 4:3 picture format. If an insertion picture which is likewise present in the 4:3 format is inserted into the actual video picture, then the insertion picture, after a decimation which maintains the aspect ratio, can be represented in a format-filling manner in the window without the insertion picture having to be compressed or stretched in a picture direction. The format of the screen is unimportant here.
If a broadcast in the 16:9 format is represented in the insertion picture, then black bars appear at the top and bottom edges of the insertion picture in the window, for the reasons mentioned above. These bars are disturbing to a viewer of the screen, particularly as they crop up in the actual video picture. The bars cover regions of the actual video picture with a picture content of the insertion picture which generally contains no information of interest to the viewer.